import java.util.Arrays;
import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        int n = in.nextInt();
        in.nextLine();
        int[] arr = new int[n * 3];
        for (int i = 0; i < 3 * n; i++) {
            arr[i] = in.nextInt();
        }
        Arrays.sort(arr);
        int j = arr.length - 2;
        int count = 0;
        for (int k = 0; k < n; k++) {
            count += arr[j];
            j -= 2;
        }
        System.out.println(count);
    }
}